Citus

Judgement

What it is

Building block

What it does

A PostgreSQL extension that shards tables across a cluster of Postgres nodes and runs queries in parallel, with reference tables replicated to every node.

Adopt it when

A multi-tenant SaaS or analytics workload has outgrown a single Postgres server and you want to stay on Postgres.

Watch out

AGPL-3.0, and sharding needs careful choice of distribution keys; Microsoft offers it managed on Azure.

Ready for

Production-ready

Runs as

Self-hosted server and cloud service

Built with

C and PostgreSQL

How established

Established: started 10 years ago, latest release v14.3.0.

What the license allows

Use inside your business is unrestricted. If you change it and let customers use it over the internet, you must publish your changes.

Judged on 2026-11-03 from the project's README and GitHub data. The license and age lines are worked out directly.

Built from

Follow it down: Citus → GCC → LLVM project → runs on a microchip

How compilers were built, back to punched paper tape

Open-source alternatives to Citus

1. 1
   Prometheus prometheus

   The Prometheus monitoring system and time series database.

   Complete system Production-ready You run services or Kubernetes and need metrics and alerting with the de facto standard toolset.

   ★ 67k Apache-2.0 Go Active, pushed today
2. 2
   Etcd etcd-io

   Distributed reliable key-value store for the most critical data of a distributed system

   Building block Production-ready You need a small amount of critical coordination data kept consistent across a cluster.

   ★ 52k Apache-2.0 Go Active, pushed today
3. 3
   ClickHouse ClickHouse

   ClickHouse® is a real-time analytics database management system

   Building block Production-ready You need fast analytics on large append-heavy data such as events, logs or metrics.

   ★ 51k Apache-2.0 C++ Active, pushed today
4. 4
   Milvus milvus-io

   Milvus is a high-performance, cloud-native vector database built for scalable vector ANN search

   Building block Production-ready You need vector search over hundreds of millions of embeddings or more and have the people to run a distributed system.

   ★ 47k Apache-2.0 Go Active, pushed today
5. 5
   DuckDB duckdb

   DuckDB is a high-performance analytical database system

   Building block Production-ready You analyse data that fits on one machine and want fast SQL without running a server.

   ★ 43k MIT C++ Active, pushed today
6. 6
   TiDB pingcap

   TiDB is built for agentic workloads that grow unpredictably, with ACID guarantees and native support for transactions, analytics, and vector search. No data silos. No noisy neighbors. No infrastructure ceiling.

   Building block Production-ready You run MySQL workloads that have outgrown one server and need to scale out without manual sharding.

   ★ 41k Apache-2.0 Go Active, pushed today
7. 7
   Qdrant qdrant

   Qdrant - High-performance, massive-scale Vector Database and Vector Search Engine for the next generation of AI. Also available in the cloud https://cloud.qdrant.io/

   Building block Production-ready You are building semantic search, RAG or recommendations and want a dedicated vector store that is simple to self-host.

   ★ 35k Apache-2.0 Rust Active, pushed today
8. 8
   Cognee topoteretes

   Cognee is the open-source AI memory platform for agents. Give your AI agents persistent long-term memory with small models for free

   Building block Usable You build agents that need long-term memory across sessions and want graph-based retrieval rather than plain vector RAG.

   ★ 33k Apache-2.0 Python Active, pushed today

Commercial databases

1. 1
   Snowflake Snowflake Inc.

   Snowflake powers AI, data engineering, applications, and analytics on a trusted, scalable AI Data Cloud—eliminating silos and accelerating innovation.

   Complete system Production-ready A company has many data sources to combine for analytics and wants a managed warehouse that scales without tuning.

   6.5k readers a month Since 2012 Commercial
2. 2
   MongoDB Atlas MongoDB, Inc.

   Build AI applications and agents on MongoDB Atlas platform, the #1 modern, run anywhere platform that brings together real-time data, intelligent retrieval, and governed action.

   Building block Production-ready Your app suits a JSON document model and you want MongoDB without running it yourself.

   4.1k readers a month Since 2009 Commercial
3. 3
   Oracle Database Oracle Corporation

   Proprietary database management system

   Building block Production-ready A large enterprise runs software that requires Oracle, or needs its high-end availability features.

   2.2k readers a month Since 1979 Commercial
4. 4
   Microsoft SQL Server Microsoft

   SQL Server 2025 redefines what's possible for enterprise data. With developer-first features and integration with analytics and AI models, SQL Server 2025 accelerates AI innovation using the data you already have.

   Building block Production-ready Your business runs .NET applications or vendor software that requires SQL Server.

   945 readers a month Commercial
5. 5
   Google BigQuery Google

   BigQuery is the autonomous data and AI platform, automating the entire data life cycle so you can go from data to AI to action faster.

   Complete system Production-ready You are on Google Cloud or export GA4 data and want SQL analytics without managing servers.

   313 readers a month Since 2010 Commercial
6. 6
   InfluxDB Cloud InfluxData

   InfluxDB 3 is the leading time series database to collect, organize, and act on massive volumes of high-resolution data in real-time.

   Building block Production-ready You collect high-volume IoT or monitoring metrics and want a purpose-built time-series store you do not run yourself.

   298 readers a month Since 2013 Commercial